The use of transparent glazing materials utilizing polycarbonate resin as a structural component for windows, windshields and the like are well known. While these polycarbonate resins are easily fabricated into the desired shape and have excellent physical and chemical properties, such as being less dense than glass and having more breakage resistance than glass, their abrasion resistance and chemical solvent resistance is relatively low.
In order to overcome this relatively low scratch and mar resistance and to otherwise improve the surface characteristics of the molded substrate, various coatings have been applied to the polycarbonate resins. U.S. Pat. No. 3,582,398 describes a fabricated polycarbonate part having improved optical properties consisting of a polycarbonate substrate and a transparent coating thereon of a thermoplastic polymethyl-methacrylate. Additionally U.S. Pat. No. 4,061,652 describes a coating for polycarbonates comprised of (i) an acrylic resin which is a mixture of olefinically unsaturated organic monomers in combination with an acrylic polymer; and (ii) certain urethanes of hydroxybenzotriazoles and hydroxybenzophenones in combination with certain catalysts. U.S. Pat. Nos. 3,451,838, 3,986,997 and 4,027,073 disclose organopolysiloxane coating compositions and techniques for the application of these organopolysiloxane coatings onto polycarbonate surfaces. While these coatings have many desirable properties, e.g., they are hard, abrasion resistant, and chemical solvent resistant, these organopolysiloxane coatings do not in all instances possess the requisite degree of uniform adherence to and durability on these polycarbonate surfaces. U.S. Pat. No. 3,707,397 describes a process for providing a hard coating on, inter alia, polycarbonate articles, said process including priming the polycarbonate surface with an adhesion promoting thermosettable acrylic and applying an organopolysiloxane onto the primed surface. An article produced by this process, while possessing acceptable initial adherence of the organopolysiloxane to the substrate, suffers from the disadvantage that upon prolonged exposure to weathering, and particularly to sunlight, the organopolysiloxane generally tends to lose its initial adherence to the substrate. Furthermore, as the thickness of the thermoset acrylic primer layer increases, the abrasion resistance of the coated article generally decreases. There thus remains a need for non-opaque polycarbonate articles having uniformly, tenaciously and durably adhered abrasion and chemical resistant coatings thereon, and it is a primary object of the present invention to provide such articles and a relatively simple and economical process for producing these articles.